1. Field of the Invention
The present invention relates to a projector, and more particularly, to a projector capable of protecting retinas from projection light.
2. Description of the Background Art
In a projector, light of three primary colors, i.e., red light, green light, and blue light, are normally used as a light source for achieving color display. A cathode-ray tube (CRT), a halogen lamp, a xenon lamp, a metal halide lamp, an extra-high pressure mercury lamp, and the like have been used as the light source thereof. Recently, along with growing awareness of energy conservation, projectors using light emitting diodes (LEDs) and laser capable of reducing power consumption as a light source have also appeared on the market.
As to the above-mentioned projector, attention should be paid to effects of blue light on retinas. It is known that in a case where retinas are exposed to the light having a wavelength of mainly 400 nm to 500 nm, molecules in cells are excited by light and cause a chemical reaction, and accordingly, retinal tissues are affected. Also in JIS C 7550 “Photobiological safety of lamps and lamp systems” (2011) of the Japan Industrial Standards, exposure to blue light is limited by, for example, providing an allowed exposure time for blue light to prevent retinas from being affected by blue light.
For example, a blue LED known as a light source of a display device has spectral characteristics in a wavelength range that affects retinas, and blue light does not appear bright for human eyes, and thus, the properties thereof that pupils close partially and a defense reaction by blinking does not work effectively are pointed out.
Projectors in which blue LEDs are used as a light source have already been developed. Further, in recent years, projectors in which blue laser having higher directivity and coherence than LEDs is used as a light source are being developed, which leads to an increasing possibility that retinas of a user may be affected by blue light.
Japanese Patent Application Laid-Open No. 2008-311532 discloses the technology of obtaining a white light emitting device that removes the light in a wavelength range that may have effects on retinas to lessen such effects.
Japanese Patent Application Laid-Open No. 2006-330447 discloses a projector having a retina projection mode in which control is made so as to limit an emission amount of projection light for reducing a possibility that retinas of a person who intentionally or unintentionally looks into an optical system part such as a projection lens may be affected.
It is possible to reduce a possibility that retinas may be affected with the use of a light source, from which the light in the wavelength range that may cause blue light to affect retinas is removed with an optical filter, as disclosed in Japanese Patent Application Laid-Open No. 2008-311532, but image quality inevitably degrades, for example, color reproduction range of a projected image becomes narrow.
In the retina protection mode as disclosed in Japanese Patent Application Laid-Open No. 2006-330447, the protection can be taken against a case where a person looks into projection light, but protection cannot be taken against a case where a person views a video image projected onto a screen for a long period of time.